J Syst Evol ›› 2023, Vol. 61 ›› Issue (6): 1091-1101.DOI: 10.1111/jse.12942

• Research Articles • Previous Articles    

A new red alga preserved with possible reproductive bodies from the 518-million-year-old Qingjiang biota

Rui-Yun Li1,2,3, Lin-Hao Cui1, Dong-Jing Fu1, and Xing-Liang Zhang1*   

  1. 1 State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life and Environments, Department of Geology, Northwest University, Xi'an 710069, China;
    2 Northwest University Museum, Northwest University, Xi'an 710069, China;
    3 State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, CAS, Nanjing 210008, China
    *Author for correspondence. E-mail: xzhang69@nwu.edu.cn
  • Received:2022-10-21 Accepted:2022-12-07 Online:2022-12-15 Published:2023-11-01

Abstract: Macroalgae have been a key ecological component of marine ecosystems since the Proterozoic period and are common fossil forms in Cambrian Burgess Shale-type Lagerstätten. However, in most cases, it is difficult to place these early fossil algae into modern groups because little distinctive morphology is preserved. Here, we describe a new form of macroalgae, Qingjiangthallus cystocarpium gen. & sp. nov., from the Qingjiang biota of South China. The new taxon is represented by 546 specimens remarkably preserved with characteristics that allow a phylogenetic placement into crown groups of red algae. Centimeter-sized thalli resemble members of the extant Rhodymeniophycidae (a subclass of the class Florideophyceae), and hence suggest a florideophycean affinity, which indicates that ahnfeltiophycidaen and rhodymeniophycidaen algae may have diverged at least 518Ma, accordant with estimations of molecular studies. The presence of possible cystocarps on Qingjiangthallus thalli suggests that evolutionary innovation of a triphasic life cycle in red algae may have occurred no later than the Early Cambrian. The branching patterns and branch width of Qingjiangthallus are consistent with the coarsely dichotomously branched morphogroup, which was previously present in the Ediacaran, Ordovician, and afterward, but absent in the Cambrian.

Key words: reproductive structure, Cambrian, evolutionary innovation, macroalgae, Qingjiang biota, Qingjiangthallus